EP 0 116 743 A1, EP 0 116 744 A1 and EP 0 180 543 A1 disclose methods and devices for sealing such capsules having hard shell coaxial cap and body parts which overlap when telescopically joined. The process employed comprises the steps of dipping batches of the capsules randomly oriented in mesh baskets or oriented with their cap parts upright into a sealing fluid making capillary action within the overlap of the cap and body parts or spraying the sealing fluid or steam thereof onto the seam of the overlap, removing the sealing fluid from the surface of the capsules by an air blower, and applying thermal energy to the capsules while conveying the baskets through a dryer. The documents disclose the use of a wide range of sealing fluids and specific temperatures and modes of application of thermal energy, the disclosure of which is incorporated herein by reference.
EP 1 072 245 A1 also discloses a method for sealing telescopically joined capsules with coaxial body parts through subsequent application of a sealing liquid by the overlapping region at the joint between a cap and a body, the removal of excess sealing liquid, and the application of thermal energy for drying purposes. This document particularly describes the steps of applying a sealing liquid including a solvent uniformly to the external edge of the gap of a capsule to be sealed to form a liquid ring around the circumference of the capsule, removing excess sealing liquid from the exterior of the capsule and drying the capsule by applying thermal energy from outside while gently tumbling and conveying the capsule on a spiral path. Spray nozzles are used for individually applying the sealing liquid. The excess solution is removed from around the capsule by vacuum suction or air jets. The disclosure of this document is incorporated herein by reference, too.
The prior systems for sealing capsules are partly imperfect as regards the quality of the seal and the controllability of the process parameters influencing the quality of the seal.